The bumps are arranged in a spiral path, starting at the
center of the disc. The CD player spins the disc while the
laser assembly moves outward from the center of the CD.
At a steady speed, the bumps move past any point at the outer
edge of the CD more rapidly than they move past any point
nearer the CD's center. In order to keep the bumps moving past
the laser at a constant rate, the player must slow the
spinning speed of the disc as the laser assembly moves
outward.